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EP 3 372 324 B1 |
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EUROPEAN PATENT SPECIFICATION |
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Mention of the grant of the patent: |
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18.11.2020 Bulletin 2020/47 |
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Date of filing: 05.03.2018 |
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International Patent Classification (IPC):
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LONG CARTRIDGE CASE
LANGE PATRONENHÜLSE
DOUILLE DE CARTOUCHE LONGUE
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Designated Contracting States: |
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AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL
NO PL PT RO RS SE SI SK SM TR |
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Priority: |
07.03.2017 US 15451717
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Date of publication of application: |
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12.09.2018 Bulletin 2018/37 |
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Proprietor: National Machinery LLC |
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Tiffin, OH 44883-0747 (US) |
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Inventors: |
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- CARPER, Jeffrey, W
Tiffin, OH Ohio 44883 (US)
- SNAVELY, Christopher, W
Republic, OH Ohio 44867 (US)
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Representative: Findlay, Alice Rosemary |
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Reddie & Grose LLP
The White Chapel Building
10 Whitechapel High Street London E1 8QS London E1 8QS (GB) |
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References cited: :
RU-C1- 2 113 309 US-A- 2 891 298 US-A1- 2014 083 319
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US-A- 2 748 464 US-A- 5 130 207 US-A1- 2014 298 979
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Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
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[0001] The invention relates to the manufacture of cartridge cases.
[0002] Brass cases for firearm cartridges are conventionally made in numerous steps and
on successive machines. Traditionally, cases are formed from brass strip stock that
is cupped and then drawn in multiple stages. Annealing steps between the drawing stages
are ordinarily required, especially where relatively long cases, such as rifle cases,
are being manufactured. The strip stock method produces a high scrap ratio, requires
energy for annealing, is slow and prone to dimensional variability, and occupies considerable
floor space.
[0003] It is known to cold form hollow thin wall intermediate blanks for cartridge cases
from solid wire. This process reduces scrap and, when applied to relatively short
cartridge cases, can potentially eliminate a need to anneal the blank.
[0004] Relatively long cartridge cases, for example those having a length greater than 2-1/2
times their diameter, can require in prior art practice, at least one, if not many,
annealing steps before the case can be finally drawn. Without adequate prior annealing,
the case tube wall can tear during a draw operation because of work hardening developed
during a previous draw or draws. Annealing procedures increase the cost of manufacture,
which includes that associated with equipment, energy, time delay, and labor.
[0005] US 2014/0298979 discloses a method for producing a gun cartridge casing in a single multiple station
deep drawing transfer press.
[0006] US 2014/083319 A1, on which the preamble of claim 1 is based, discloses a method for producing a cartridge
case.
[0007] US 2,891,298, on which the preamble of claim 4 is based, discloses a method of cold shaping partitioned
tubular steel articles.
[0008] The invention is defined by the claims.
[0009] The invention provides a method and tooling for forming relatively long, thin wall
cartridge case blanks from wire stock without an intermediate annealing step. The
invention utilizes a set of progressive tools in a cold forming machine to backward
extrude the blank tube in multiple steps. It has been discovered that work hardening
of the blank tube wall can be reduced using the multiple backward extrusion technique.
Consequently, a fully drawn tube wall thickness can be obtained without requiring
a prior annealing step or steps of the blank.
[0010] The inventive technique reduces work hardening in the blank tube wall from what occurs
in prior art multiple draw practice. The invention limits the plastic strain or deformation
to only the section of tube wall length formed in a single backward extrusion step.
A tube wall length section previously extruded is not further deformed and work hardened
when a subsequent length section is backward extruded. The inventive technique thus
achieves a long cartridge case blank that can be finish drawn to a tube wall thickness
that heretofore required annealing between conventional drawing processes.
[0011] The invention will now be further described by way of example with reference to the
accompanying drawings, in which:
FIGS. 1A - 1E diagrammatically illustrate a cartridge case blank forming process embodying
the invention;
FIG. 2 is a cross-sectional view of a fully drawn cartridge case blank that has been
trimmed to a desired length; and
FIG. 3 illustrates exemplary tooling employed in a progressive cold forming machine
to perform the process depicted in FIGS. 1A - 1E.
[0012] Following is a description, with reference alternatively between FIGS. 1A-1E and
FIG. 3 of basic process steps used in the manufacture of a cartridge case blank 10.
An initial blank 10 is cut from wire stock 11 by a shear at a cutoff station 12 (FIG.
3) of a progressive cold forming machine 14. The machine 14 is of a construction known
in the industry, shown, for example, in
U.S. patent 4,898,017, and discussed in greater detail below. The initial blank 10 has the shape of a solid
cylinder ordinarily with minor distortion at its sheared end faces. Typically, the
wire stock 11 is brass, although other alloys and metals can be used. An example of
a suitable brass is CDA 260. The blank 10 is transferred to a workstation shown as
a first workstation 16 where it is backward extruded to produce a tube length section
17 (FIG. 1A) of about 1/3 of a final pre-drawn tube length. The blank 10 is then transferred
to a second or subsequent workstation 18 where it is backward extruded to add another
length section 19 of a length of about 1/3 of a final pre-drawn tube length and with
an inside diameter smaller than the inside diameter of the first length section 17.
Thereafter, the blank 10 is transferred to a third or subsequent workstation 20 where
it is backward or reverse extruded a third time to add a length section 21 of about
1/3 of a final pre-drawn tube length with an inside diameter smaller than that of
the preceding length section 19. The blank 10 can be transferred to a fourth or subsequent
workstation 22 where it can be finish drawn through two draw dies 23 with a draw punch
24 or mandrel to a finished wall thickness of preferably about 0.2 mm to about 0.5
mm and more preferably about 0.3 mm measured where the blank tube designated 25 is
to be trimmed to form a mouth 27 (FIG. 2).
[0013] Preferably, after multiple backward extrusion steps, only one drawing step need be
performed on a blank to reach a final or finished wall thickness and pre-trim length
in the tube section 25 as shown in FIG. 1E. The blank 10, as described, is drawn to
a final non-trimmed tube length and tube wall thickness dimension prior to any bottling
(necking) and tapering without requiring an annealing step or steps. By way of example,
a single annealing procedure can require a brass blank to be heated to 500-700 degrees
F. for 30-45 minutes or more, for instance, to relieve an existing work hardened condition
and then require a suitable cooling off period.
[0014] Traditionally, a cartridge case has a tapered inside diameter associated with a tube
wall thickness that reduces away from a cartridge head 26 towards the open end. The
draw punch 24, as is conventional, may have a tapered profile that matches the finished
interior profile of the cartridge case. A preferred feature involves shaping the stages
of the backward extruded sections 17, 19, 21 of the blank tube 25 so that the transition
lines or steps from one diameter to the next preferably lie in close proximity to
the profile of the draw punch 24 (and ultimately the complementary varying inside
diameter of the drawn casing blank tube 25). This preferred arrangement is depicted
in FIGS. 1D and 1De, the latter being an enlargement of the drawing area indicated
in FIG. 1D. When the draw tool or punch 24 is first seated in the backward extruded
sections 17, 19, 21 as shown in FIG. 1D, two beneficial conditions exist. Lubricant
30 is trapped in the clearance spaces between the tool 24 and blank 10. Surface friction
is reduced by the small local areas of contact between the blank inside surface and
the tool 24 preceding relative movement of the draw dies 23 over the tube wall and
tool 24. These conditions are favorable to the drawing operation by reducing forces
between the draw dies 23 and the blank tube section 25 and thereby reducing the tendency
of the blank tube section to tear.
[0015] FIG. 1E illustrates a drawn cartridge case 10 with a characteristic irregular edge
31 at its open end. FIG. 2 illustrates the drawn cartridge case blank 10 after the
irregular edge 31 has been trimmed away producing an L/D (diameter) ratio of typically
at least 3. Ordinarily, as mentioned, the wall thickness of a blank measured at a
trimmed end of the tube section 25 will be about 0.4 mm or less. Preferably, the length
of the tube section trimmed away is not more than about 1/8 of the remaining trimmed
length L.
[0016] FIG. 3 is a diagrammatic representation of the progressive cold forming machine 14
in plan view in which tooling, outlined above, for practicing the invention is mounted.
The machine 14 includes a stationary bolster or die breast schematically indicated
at 37 and a ram or slide schematically illustrated at 38. The ram 38 reciprocates
towards and away from the die breast 37 and is shown at front dead center, closest
to the die breast, in FIG. 3. Wire stock 11 is fed to the cutoff station 12 where
a length of stock is sheared to form the blank 10. The four workstations 16, 18, 20,
22 are shown to the left of the cutoff station 12. As is known in the industry, the
blank 10 is successively transferred from station-to-station by a transfer mechanism
(not shown) during cyclic periods that the ram 38 is away from the die breast 37.
[0017] At the first station 16, the blank 10, received in a die 43 that is slightly larger
(e.g. 0.02 - 0.05 mm) in diameter than the blank, is backward extruded by a punch
44 of a first diameter to produce the first tube length section 17 with an inside
diameter determined by the punch. Typically, at each backward extrusion, the blank
outside diameter will grow radially to essentially the inside diameter of the associated
die. The punch and die tools 44, 43, can be sized and otherwise configured to produce
a tube wall thickness of, by way of example, between about 0.5 mm and about 1 mm in
the first section 17.
[0018] At the second station 18, the blank 10 is received in a die 46 and is backward extruded
by a punch 47. The die 46 preferably has an inside diameter slightly larger (e.g.
0.02 - 0.05 mm) than the outside diameter of the blank 10 being received from the
previous or first station 16. The diameter of the punch 47 is somewhat less than that
of the first punch 44 preferably so as to closely follow the geometry of the draw
punch. The die 46 and punch 47 are arranged for the blank to be backward extruded
to form the tube wall section 19 having an inside diameter somewhat smaller than that
of the first-formed wall section 17, as determined by the punch 47, and a length again
about 1/3 of a pre-drawn tube length. At the third station 20, the blank is received
in a die 48 and is backward extruded by a punch 49. As before, the die 48 preferably
has an inside diameter slightly larger (e.g. 0.02 - 0.05 mm) than the outside diameter
of the blank received from the preceding station 18. The diameter of the punch 49
is somewhat less than that of the preceding punch 47 as described previously to preferably
closely follow the geometry of the draw punch. The die 48 and punch 49 are arranged
for the blank to be backward extruded to form the third tube section 21 with an inside
diameter as determined by the punch 49, somewhat smaller than the inside diameter
of the second tube section 19. The punch and die tooling at the stations 16, 18 and
20 is preferably carbide.
[0019] It is preferable to configure the punch and die sets so that the inside diameter
of the tube sections before drawing of the blank at the steps between successive backward
extrusions of the tube sections is about the same or slightly larger, e.g. up to about
0.75 mm, than a diameter of the draw punch at the same axial location from the blank
head when the draw punch is seated against the bottom of the pre-drawn blank. In other
circumstances, the method can be successfully practiced without developing a close
correspondence of the backward extrusion steps and the contour of the draw punch or
tool. Generally, with a succeeding backward extruding punch and die set, the die will
have an inside diameter larger than that of the die of the preceding backward extruding
punch and die set and the punch will have an outside diameter smaller than that of
the punch of the preceding backward extruding punch and die set.
[0020] The blank 10 with a tube formed by multiple backward extrusions is transferred to
the draw station 22 where it is drawn, for example, through the two draw dies 23 by
the draw punch 24 carried on the ram 38. The resulting tube can be considered finished
or fully drawn at this station 22.
[0021] The foregoing describes forming steps and tooling capable of producing a relatively
long cartridge case tube that can be finally or finish drawn without the need to anneal
the blank before the final drawing step is performed. It is difficult to precisely
characterize a long cartridge case by length (trimmed length) to diameter (outside
diameter) ratio, although some analysis of common ammunition would specify a ratio
greater than 2-1/2, preferably of about 3 to 1 or greater and, more preferably, a
ratio of about 3.2 to 1 or greater. Regardless of length to diameter ratio, multiple
reverse extrusion steps are useful in the manufacture of cartridge cases that would
otherwise require annealing before finish drawing to prevent tearing of the tube section.
[0022] The process described in reference to FIGS. 1A - 1E and FIG. 3, is less involved
for purposes of clarity than what can be performed in one or tandem cold-forming machines.
The forming machine 14 may have additional workstations with related tooling before,
beyond, or intervening those described and/or can include additional forming features
in the illustrated stations 16, 18, 20 and 22 and tooling used at these stations.
The head 26 of the blank 10 is shown closed and if pierced for a flash hole can be
considered effectively closed. In some instances, multiple backward extrusion to avoid
tearing failure at a finish draw without a preceding annealing process may be accomplished
with two backward extrusions or more than three backward extrusions. It will be understood
that the finally drawn blank may be annealed to enable the cartridge tube to be bottled
(necked) and/or tapered.
[0023] It should be evident that this disclosure is by way of example and that various changes
may be made by adding, modifying or eliminating details, without departing from the
scope of the appended claims.
1. A method of producing a long cartridge case blank comprising cutting a length of wire
(11) from a supply to initially form a blank (10), forming a circular tube (17, 19,
21) from one end of the blank by backward extrusion, characterised in that the blank tube is formed by at least three separate backward extrusion steps, wherein
each successive backward extrusion step is performed (47, 49) with a punch that is
smaller in diameter than a punch (44, 47) used in the preceding extrusion step with
the result that the blank tube is formed with three separate sections (17, 19, 21)
of progressively smaller inside diameter.
2. A method as set forth in claim 1, wherein said three backward extrusion steps are
performed on the same machine.
3. A method as set forth in claim 2, wherein the backward extruded blank is finish drawn
on said same machine.
4. A kit of punches and dies for shaping tubes of long cartridge case blanks (10) in
a progressive forming machine, wherein the kit comprises circular punch and die sets
(44, 43, 47, 46, 49, 48), each set being configured to backward extrude a blank tube
section, characterised in that the kit comprises at least three sets (44, 43, 47, 46, 49, 48), a second one of said
sets (47, 46) being proportioned to receive and backward extrude a blank formed in
a first one of said sets (44, 43), and a third one of said sets (49, 48) being proportioned
to receive and backward extrude a blank formed in said second set (47, 46), and in that the sets are configured and arranged to collectively produce an intermediate blank
having three axially extending stepped inside cylindrical surfaces (17, 19, 21) between
an open end and an effectively closed end of the blank tube, a small diameter one
of said cylindrical surfaces (17) being adjacent the effectively closed end and a
large one of said cylindrical surfaces (21) being adjacent the open end.
5. A kit as set forth in claim 4, including a draw punch (24), the sets of punches and
dies (44, 43, 47, 46, 48) being constructed and arranged to form a pre-drawn blank
with an inside stepped cylindrical tube with steps (17, 19, 21) between successive
backward extrusions being closely adjacent or in contact with the exterior of the
draw punch (24) when the draw punch is seated in said pre-drawn blank.
1. Verfahren zum Herstellen eines langen Patronenhülsenrohlings, umfassend das Abschneiden
eines Drahtstücks (11) von einem Vorrat zum Urformen eines Rohlings (10), Formen einer
ringförmigen Röhre (17, 19, 21) von einem Ende des Rohlings durch Rückwärts-Strangpressen,
dadurch gekennzeichnet, dass die Rohlingsröhre durch wenigstens drei separate Rückwärts-Strangpressschritte geformt
wird, wobei jeder nachfolgende Rückwärts-Strangpressschritt mit einem Stempel durchgeführt
wird (47, 49), der einen kleineren Durchmesser als ein Stempel (44, 47) hat, der im
vorangehenden Strangpressschritt verwendet wird, mit dem Ergebnis, dass die Rohlingsröhre
mit drei separaten Abschnitten (17, 19, 21) mit nacheinander kleinerem Innendurchmesser
geformt wird.
2. Verfahren nach Anspruch 1, wobei die genannten drei Rückwärts-Strangpressschritte
an derselben Maschine durchgeführt werden.
3. Verfahren nach Anspruch 2, wobei der rückwärts-stranggepresste Rohling an derselben
Maschine fertiggezogen wird.
4. Stempel- und Matrizengarnitur zum Umformen von Hülsen langer Patronenhülsenrohlinge
(10) in einer Stufenumformmaschine, wobei die Garnitur ringförmige Stempel- und Matrizensätze
(44, 43, 47, 46, 49, 48) umfasst, wobei jeder Satz zum Rückwärts-Strangpressen eines
Rohlingsröhrenabschnitts gestaltet ist, dadurch gekennzeichnet, dass die Garnitur wenigstens drei Sätze (44, 43, 47, 46, 49, 48) umfasst, ein zweiter
der genannten Sätze (47, 46) zum Aufnehmen und Rückwärts-Strangpressen eines in einem
ersten der genannten Sätze (44, 43) geformten Rohlings proportioniert ist und ein
dritter der genannten Sätze (49, 48) zum Aufnehmen und Rückwärts-Strangpressen eines
in dem genannten zweiten Satz (47, 46) geformten Rohlings proportioniert ist und dass
die Sätze gestaltet und angeordnet sind, um zusammen einen Zwischenrohling zu ergeben,
der drei sich axial erstreckende, abgestufte zylindrische Innenflächen (17, 19, 21)
zwischen einem offenen Ende und einem effektiv geschlossenen Ende der Rohlingsröhre
hat, wobei eine der genannten zylindrischen Flächen (17) mit einem kleinen Durchmesser
an das effektiv geschlossene Ende angrenzt und eine große der genannten zylindrischen
Flächen (21) an das offene Ende angrenzt.
5. Garnitur nach Anspruch 4 mit einem Ziehstempel (24), wobei die Stempel- und Matrizensätze
(44, 43, 47, 46, 48) aufgebaut und angeordnet sind, um einen vorgezogenen Rohling
mit einer innen abgestuften zylindrischen Röhre mit Stufen (17, 19, 21) zwischen aufeinanderfolgenden
Rückwärts-Strangpressungen zu formen, die eng angrenzend an das oder in Kontakt mit
dem Äußere(n) des Ziehstempels (24) sind, wenn der Ziehstempel in dem genannten vorgezogenen
Rohling sitzt.
1. Procédé de production d'une ébauche de douille de cartouche longue comprenant couper
une longueur de fil métallique (11) d'un approvisionnement pour former initialement
une ébauche (10), former un tube circulaire (17, 19, 21) d'une extrémité de l'ébauche
par filage avec remontée de matière, caractérisé en ce que le tube d'ébauche est formé par au moins trois étapes séparées de filage avec remontée
de matière, où chaque étape successive de filage avec remontée de matière est effectuée
(47, 49) avec un poinçon qui est plus petit en diamètre qu'un poinçon (44, 47) utilisé
à l'étape de filage précédente avec le résultat que le tube d'ébauche est formé avec
trois sections séparées (17, 19, 21) de diamètre intérieur progressivement plus petit.
2. Procédé selon la revendication 1, dans lequel lesdites trois étapes de filage avec
remontée de matière sont effectuées sur la même machine.
3. Procédé selon la revendication 2, dans lequel l'ébauche filée avec remontée de matière
est étirée à finition sur ladite même machine.
4. Kit de poinçons et de filières pour façonner des tubes d'ébauches de douilles de cartouche
longues (10) dans une machine de formage progressif, où le kit comprend des jeux de
poinçons et filières circulaires (44, 43, 47, 46, 49, 48), chaque jeu étant configuré
pour filer avec remontée de matière une section de tube d'ébauche, caractérisé en ce que le kit comprend au moins trois jeux (44, 43, 47, 46, 49, 48), un deuxième desdits
jeux (47, 46) étant proportionné pour recevoir et filer avec remontée de matière une
ébauche formée dans un premier desdits jeux (44, 43), et un troisième desdits jeux
(49, 48) étant proportionné pour recevoir et filer avec remontée de matière une ébauche
formée dans ledit deuxième jeu (47, 46), et en ce que les jeux sont configurés et arrangés pour produire collectivement une ébauche intermédiaire
ayant trois surfaces cylindriques intérieures étagées s'étendant axialement (17, 19,
21) entre une extrémité ouverte et une extrémité effectivement fermée du tube d'ébauche,
un petit diamètre d'une desdites surfaces cylindriques (17) étant adjacent à l'extrémité
effectivement fermée et un grand diamètre desdites surfaces cylindriques (21) étant
adjacent à l'extrémité ouverte.
5. Kit selon la revendication 4, comprenant un poinçon à étirer (24), les jeux de poinçons
et de filières (44, 43, 47, 46, 49, 48) étant fabriqués et arrangés pour former une
ébauche préétirée avec un tube cylindrique étagé intérieur (17, 19, 21) entre des
filages avec remontée de matière successifs étant étroitement adjacents ou en contact
avec l'extérieur du poinçon à étirer (24) lorsque le poinçon à étirer est placé dans
ladite ébauche préétirée.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only.
It does not form part of the European patent document. Even though great care has
been taken in compiling the references, errors or omissions cannot be excluded and
the EPO disclaims all liability in this regard.
Patent documents cited in the description